详解事件代理委托

var addEvent = (function () {
 if (document.addEventListener) {
 return function (element, type, handler) {
 element.addEventListener(type, handler, false);
 };
 } else if (document.attachEvent) {
 return function (element, type, handler) {
 element.attachEvent(‘on‘ + type, function () {
 handler.apply(element, arguments);
 });
 };
 } else {
 return function (element, type, handler) {
 element[‘on‘ + type] = function () {
 return handler.apply(element, arguments);
 };
 };
 }
})(),
getClassElements = function (parentElement, classname) {
 var all, element, classArr = [], classElements = [];
 if (parentElement.getElementsByClassName) {
 return parentElement.getElementsByClassName(classname);
 } else {
 all = parentElement.getElementsByTagName(‘*‘);
 for (var i = 0, len = all.length; i < len; i++) {
 element = all[i];
 classArr = element && element.className && element.className.split(‘ ‘);
 if (classArr) {
 for (var j = 0; j < classArr.length; j++) {
  if (classArr[j] === classname) {
  classElements.push(element);
  }
 }
 }
 }
 return classElements;
 }
},
delegate = function () { // 参数：element, type, [selector,] handler
 var args = arguments,
 element = args[0],
 type = args[1],
 handler;
 if (args.length === 3) {
 handler = args[2];
 return addEvent(element, type, handler);
 }
 if (args.length === 4) {
 selector = args[2];
 handler = args[3];
 return addEvent(element, type, function (event) {
 var event = event || window.event,
 target = event.target || event.srcElement,
 quickExpr = /^(?:[a-zA-Z]*#([\w-]+)|(\w+)|[a-zA-Z]*\.([\w-]+))$/,
 match,
 idElement,
 elements,
 tagName,
 count = 0,
 len;
 if (typeof selector === ‘string‘) {
 match = quickExpr.exec(selector);
 if (match) {
  // #ID selector
  if (match[1]) {
  idElement = document.getElementById(match[1]);
  tagName = match[0].slice(0, match[0].indexOf(‘#‘));
  // tag selector
  } else if (match[2]) {
  elements = element.getElementsByTagName(selector);
  // .class selector
  } else if (match[3]) {
  elements = getClassElements(element, match[3]);
  tagName = match[0].slice(0, match[0].indexOf(‘.‘));
  }
 }
 if (idElement) {
  if ( tagName ? tagName === idElement.nodeName.toLowerCase() && target === idElement : target === idElement ) {
  return handler.apply(idElement, arguments);
  }
 } else if (elements) {
  for (len = elements.length; count < len; count++) {
  if ( tagName ? tagName === elements[count].nodeName.toLowerCase() && target === elements[count] : target === elements[count] ) {
  return handler.apply(elements[count], arguments);
  }
  }
 }
 }
 });
 }
};

<div class="animated bounceOut cc">this is our 未来！</div>
    <div class="haha" style="padding:50px;border:1px solid red;">
        
    </div>
    <script type="text/javascript" src="./main.js"></script>
    <script>
        window.delegate($(‘.haha‘)[0], ‘mouseover‘, ‘.haha1‘, function(event) {
            alert("nihao");
        });
        $(‘.haha‘).append(‘<div class="haha1" style="display: inline-block;width: 500px;height: 300px;border:1px solid black;">this is hahaboy!</div>‘);
    </script>